Apparatus for the manufacture of a refrigerant



March 6, 1934. v SHQELD 1,949,730

APPARATUS FOR THE MANUFACTURE OF A REFRIGERANT Filed Aug. 28, 1929INVENTOR. A/crnf' 6/70 9/01 m Q A TTORNE Y.

Patented Mar.

APPARATUS FOR THE MANUFACTURE OF A REFRIGERAN T Mark Shoeld, MountLebanon Township, Allegheny County, Pa., assignor to The Koppers Companyof Delaware," a corporation of Dela- Application August 28, 1929, SerialNo. 388,933

1 Claim.

This invention relates to an improved process of and apparatus foroxide.

Ordinarily,

ration of dry ice,

preparing solid carbon dicarbon dioxide used for the prepais produced byburning coke,

and the fiue gases are treated with a sodium carbonate solution whichabsorbs the carbon dioxide and is converted into sodium bicarbonate. Thebicarbonate solution is boiled and pure carbon dioxide gas is liberated.This carbon dioxide gas is compressed and liquefied. The liquid isallowed to expand through a nozzle to atmospheric pressure. During thisexpansion approximately 40% of the total carbon dioxide is precipitatedas 1 snow, the remaining carbon dioxide gas must be recompressed andliquefied before it can be encarbon dioxide.

either to treat the the carbon dioxide carbon dioxide bef the snow.

It has been found unnecessary gases chemically or to liquefy in order toseparate out pure ore it is expanded to produce In accordance with theprocess of this invention a diluted carbon dioxide gas may be compressedto a relativ lowed to expand to ely high pressure and then alor to aboutatmospheric pres- 0 sure. Depending upon the pressure used, a part orall of the carbon For the purpose dioxide is precipitated assnow. ofreducing production costs,

flue gases or waste gases containing carbon dioxide may be used.

taining approximately 25% Blast furnace stove gas concarbon dioxide andnitrogen is particularly suitable.

The process of this invention may be carried out in the manner with theapparatus shown in drawing in which:

Figure 1 is a view of the shown partly in elevation section; and

Fig. 2 is a view .of

to be described in connection the accompanyin preferred apparatus andzpartly in crossin elevation of a modification a portion of theapparatus shown in Fig. 1.

Gas containing carbon dioxide is passed through pipe 1 into the bottomof a cooler 2.

Water supplied through pipe 3 at the top of the cooler 2 is sprayeddownwardly countercurrent to the 0 gas. The water and other matterentrained therein pass out of the cooler 2 by means of pipe 4. Theresulting gases of cooler 2 through pipe 5 of a tower 6. The the tower 6throug pass out at the top and into the bottom gases pass upwardlythrough h a downward spray of dilute {chambers around the extrusiondevice.

sodium carbonate solution whereby objectionable solid-matter and gasessuch as sulphur dioxide are removed.

The dilute sodium carbonate solution is circulated by means of a pump 7through a pipe 8 90 and into the top of the tower 6.

After the above preliminary treatment, the residual gases containingcarbon dioxide are passed through a pipe 9 and through a series ofcompression pumps and coolers. The gases pass 6 successively through thefirst stage compressor 10, cooler 11, the second stage compressor 12,the cooler 13, the third stage compressor 14 and the cooler 15 andthencethrough a heat exchanger 16. From the heat exchanger 16, the compressedand cooled gases pass through pipe 17 having a valve 18, and throughnozzle 19 whereupon the gases are expanded to produce solid carbondioxide, in a combination filtering chamber and extrusion device.

The combination filter chamber and extrusion device comprisesa snowchamber in which the solid carbon dioxide is separated from residualgases, and, means for compressing the carbon dioxide particles intosolid blocks. The snow chamber has a perforated inner wall 20 and twoouter solid walls 21 and 22 spaced apart to form two annular chambers.The extrusion device is placed at the bottom of the tower and extendshorizontally therefrom and has a solid tubular wall 23 which graduallytapers to an opening 24 of relatively small diameter. The walls 21 and22 are continued so as to form two annular Within the extrusion deviceis a tapering screw, conveyor 25 which may be turned by any suitablemeans.

In the operation of the combination filter chamber and extrusion device,the carbon dioxide snow settles to the bottom of the snow chambersurrounded by the perforated wall 20. The residual gases pass throughthe perforations and the scraping means comprising a revolving shaft 26upon which are mounted scrapers 27, prevent the openings in the wall 20from becoming clogged by the carbon dioxide snow.

The carbon dioxide snow is carried away from the bottom of the snowchamber by means ofv the screw conveyor 25 which compresses it to- Wardthe small end of the tube 23 and forces it out in solid form through theopening 24 where blocks of carbon dioxide of any desired size may be cutoff. The aforesaid residual gases separated from the carbon dioxide snowpass downwardly be- 1 tween the walls 20 and 21 and thence horizontallyaround the wall 23 of the extrusion device and aid in keeping theapparatus cold. As an added precaution the annular chamber formed bywalls 21 and 22 is also continued around the extrusion device and servesas an insulating means.

The residual gases are passed through pipe 28 into the heat exchanger 16around the tubes through which the carbon-dioxide-containing gases fromthe cooler .15 are passed and out through pipe 29.

The series of apparatus shown in Fig. 2 may be substituted for theapparatus units 10 to 15, inclusive, shown in 1. In Fig. 2 a bubble tank30 is placed after the first stage compressor 31 and cooler 32 andbefore the second stage compressor 33 which is followed by a cooler 34,a third stage compressor 35 and a cooler 36.

Gases from cooler 36 may then be-passed through a freezing unit foreliminating water. Two such freezing units are shown. namely, 3'7 and 38which may be used alternately so that one may be in use while water iceis being removed from: the other. 1

From a freezing unit, the gases are passed through any suitablepre-cooler 39 from which they are passed through a heat exchanger suchas 16 and a filtering and extrusion meansas shown in Fig. 1. The freezinunits 3'7 and 38 may be maintained at a sufficiently low temperature bymeans of the gases coming from the heat exchanger 16- through pipe 29.

The bubble tank 30 may contain potassium permanganate solution for theganic matter or other obnoxious ingredients in the gas. Two such unitsmay be used alternately so that one may be placed in operation while theother is being cleaned. In place of a bubble tank containing potassiumpermanganate solution, a tower containing charcoal or activated charcoalmay be employed.

The gas before entering .dioxide separates from removal of orthe heatexchanger 16 may be compressed to about from 300 atmospheres to 500atmospheres or it may be compressed to a somewhat lower pressure of, forinstance, 100 atmospheres and cooled down by the use of a carbon dioxiderefrigerating machine. Under these conditions, a part of the carbondioxide tends to liquefy. Nevertheless, the mixture of gases and liquidmay be expanded through a nozzle to form carbon dioxide snow.

At minus '78 C. the vapor pressure of solid carbon dioxide is 760millimeters and at minus 123 C. the vapor pressure is 4 millimeters.Upon expanding the dilute carbon dioxide gas at this latter temperature,substantially all the carbon the nitrogen and other gases in the form ofa solid. A practical operating temperature is about minus 100 C. orminus 105 C. 1

The advantages of the present process are: (1) the production ofsubstantially 100% pure carbon dioxide and the manufacture of solidcarbon dioxide are combined in one simple operation, (2) norecompression of carbon dioxide is required, and (3) the carbon dioxideice is produced at a somewhat lower temperature than that used inpresent processes, which reduces the losses in handling.

I claim as my invention:

Apparatus comprising a chamber having a perforated wall, a tubeextending from the bottom of the said chamber; a plurality of spacedsolid walls encasing the sides of the said chamber and of the said tubeand forming continuous annular chambers around both; inlet means at thetop of the said first named chamber for compressed, cooled gascontaining carbon dioxide; scrapers for removing carbon dioxide snowfrom the said perforated wall; gas outlet means for withdrawing gasthrough the perforated wall and the innermost annular chamber; and ascrew conveyor for passing the carbon dioxide snow from the bottom ofthe said first named chamber through the said tube.

MARK SHOELD.

